The present invention relates generally to the heating of water for commercial and/or home use, and particularly to a water heating system that is free of the corrosive effects of galvanic action, thereby providing the system with a long life. However, fluids other than water can cause corrosion problems in systems employing metals that are galvanically different. Hence, the invention is not limited to the heating of water only.
A substantial amount of art exists which discloses the use of heat sources, such as solar heaters, to heat water within a container or tank structure, the heat source being connected in fluid communication with a heat exchanger (condenser) located within the container. This art includes the use of ordinary glass-lined, hot water tanks having a heat exchange unit within the tank structure, such as shown in U.S. Pat. No. 4,173,872 to Amthor.
However, we have discovered that in using such hot water tanks, which tanks are made from steel, in combination with a non-ferrous heat exchanger, such as a copper condenser, that galvanic processes occur between the steel of the tank and the copper of the condenser, which result in corrosive attack and penetration of the wall of the tank. This is particularly true when there is a small pinhole-type of perforation in the glass lining of the tank, such that the relatively large copper heat exchanger "sees" a very tiny steel element. The result of this is a highly concentrated attack on the small area of steel behind the pinhole in the glass.
In addition, we have found that the use of sacrificial anodes disposed within the tank and in the water within the tank are not sufficient to prevent rapid corrosion and deterioration of the tank wall. What is therefore needed is the outright prevention of such galvanic action.